An awful outdated system still used in many countries such as the US and partly in the UK.

Revolves around measuring weight, length, distance and currency in units that actually do not make sense, unlike the metric system which has been taken on board by most countries and is used in all science.

imperial system : 12 inches is a foot. 3 foot is a yard. 1760 yards is a mile.

metric system : 10 milimetres is a centimetre. 100 centimetres is a metre. 1000 metres is a kilometre.

Seriously, metric works for scienfitc calculations. But - when did you last have to work out the weight of an inch of rain falling on an acre (versus a centimetre of rain on a hectare!).

Goliath was six cubits and a span; those Imperial units equate - in other Imperial units - to an improbabble nine foot eight tall.
Now, the metric equivalent is 2,95m (equally improbable, but not blindingly obvious to a lay man).
"The Imperial system relates to human beings, and the things they are familiar with," said Nichola to her pal Nic; "It can be used for recondite scientific calculations, but metric may well be better for those."